High-temperature superconductivity and antiferromagnetism in multilayer cuprates: 63Cu and 19F NMR on five-layer Ba 2Ca 4Cu 5O 10(F,O) 2

Abstract

We report systematic Cu and F NMR measurements of five-layered high-T c cuprates Ba 2Ca 4Cu 5O 10(F,O) 2. It is revealed that antiferromagnetism (AFM) uniformly coexists with superconductivity (SC) in underdoped regions, and that the critical hole density p c for AFM is ∼0.11 in the five-layered compound. We present the layer-number dependence of AFM and SC phase diagrams in hole-doped cuprates, where p c for n-layered compounds p c(n) increases from p c(1) ∼ 0.02 in La 2-xSr xCuO 4 or p c(2) ∼ 0.05 in YBa 2Cu 3O 6+y to p c(5) ∼ 0.11. The variation of p c(n) is attributed to interlayer magnetic coupling, which becomes stronger with increasing n. In addition, we focus on the ground-state phase diagram of CuO 2 planes, where AFM metallic states in slightly doped Mott insulators change into the uniformly mixed phase of AFM and SC and into simple d-wave SC states. The maximum T c exists just outside the quantum critical hole density, at which AFM moments on a CuO 2 plane collapse at the ground state, indicating an intimate relationship between AFM and SC. These characteristics of the ground state are accounted for by the Mott physics based on the t-J model; the attractive interaction of high-T c SC, which raises T c as high as 160 K, is an in-plane superexchange interaction J in (∼0.12 eV), and the large J in binds electrons of opposite spins between neighboring sites. It is the Coulomb repulsive interaction U (>6 eV) between Cu-3d electrons that plays a central role in the physics behind high-T c phenomena. © 2012 American Physical Society.